OBJECTIVES: To evaluate the cost-effectiveness of dosing 5-fluorouracil (5-FU) based on pharmacokinetics instead of based on body-surface area (BSA) for patients with advanced pancreatic cancer who received FOLFIRINOX chemotherapy. METHODS: Incremental cost per life year gained (LYG) was calculated based on data collected in a multicenter retrospective observational study of patients with advanced pancreas cancer who received FOLFIRINOX as first line treatment. The perspective was that of the health-care payer and we only included direct medical costs (drugs, drug administration and monitoring, and adverse effects). Unit costs were obtained from databases and literature. To control for potential confounding variables, the propensity score (PS) method with matching was performed. Effectiveness was measured as overall survival (OS), Kaplan-Meier curves were created. OS hazard ratio (HR) was estimated with cox regression method. Incremental costs and effectiveness were estimated by bootstrap adjusting by PS. Two types of sensitivity analyses were performed, univariate and deterministic analyses, and multivariate probabilistic analysis using bootstrap techniques. RESULTS: CONCLUSIONS: Therapeutic monitoring of 5-FU entails a moderate cost increase compared to current dosing practice based on BSA, and it is a cost-effective strategy.